Pothead



P 8, 1959 J. B. o'MARA 2,903,501

POTHEAD Filed June 27, 1956 INVENT OR JOSEPH B. O MARA ATTORNEY$ United States Patent 2,903,501 POTHEAD Application June 27,1956, Serial No. 594,223

3 Claims. (Cl. 174-19) This invention relates to potheads, and is particularly directed to an improved pothead terminal assembly for cable conductors. It is the principal object of the invention to provide an improved pothead terminal assembly of the type having a metallic hood closure permanently sealed to one end of the insulator, in which tight mechanical and electrical connection of the cable connector to the hood closure is achieved without objectionable deformation of the hood, and the risk of a faulty electrical connection due to penetration of sealing compound between the hood and the cable connector is avoided.

It is important that a tight closure be provided for pothead terminal insulators, both to prevent the penetration of moisture into the interior of the insulator and to prevent escape of the sealing compound with which the insulator is filled. To this end it has become quite common in recent years to provide the pothead insulator with an end closure which is permanently attached thereto by a. metal-to-ceramic soldered seal made at the factory. This type of end closure provides particularly effective protection against leakage of moisture into, or sealing compound out of, the pothead insulator. However, it makes it dilficult to provide a secure electrical connection between the cable conductor inside the insulator and the aerial or other conductor to be connected to it outside the insulator.

It has been proposed heretofore to make the electrical connection through a thin metallic hood which can be deformed under the influence of an external connector clamp into tight engagement with the cable connector inside the insulator. A major disadvantage of pothead assemblies thus constructed has been that the sealing compound introduced into the interior of the insulator may penetrate between the cable connector and the hood and so interfere with making a good electrical connection between these parts. Another disadvantage is that the insulator assembly cannot be reused, Once the hood has been deformed by the aerial cable clamp, it is not practical to salvage the insulator without sending it back to the factory or to a special repair shop to have the old hood removed and a new one applied.

According to this invention an improved pothead terminal assembly which is free from the foregoing disadvantages is provided. The new pothead terminal assembly comprises a pothead insulator to which a cylindrical metallic hood is permanently sealed at the factory, forming an end closure thereon. A stem connector for attachment to the cable conductor, and having a cylindrical stern portion of outside diameter only slightly less than the inside diameter of thehood, is provided. The stem portion of the connector thus may easily be inserted through the insulator into the interior of the hood. The stem connector advantageously is provided at its end opposite the stem portion with a socket to receive and be electrically connected to a cable conductor; and the stern portion is slotted longitudinally throughout substantially its entire length and is formed at its free end with a tapered threaded recess. A correspondingly threaded tapered plug is provided for insertion into such recess. Thus, when the stem connector is inserted into the interior of the hood, the tapered plug may be screwed into the recess, thereby expanding the slotted stem portion of the stem connector into tight mechanical and electrical engagement with the interior cylindrical surface of the hood. The hood preferably is closed at its free outer end save for the provision of a centrally disposed vent hole, through which access may be had to permit tightening of the tapered plug and through which air is vented from the interior of the pothead insulator when sealing compound is forced therein. The vent hole may be closed by a vent hole closure screw after filling the insulator with conventional sealing compound.

The foregoing and other features of the invention are described in detail below with reference to the accom panying drawings, wherein:

Fig. 1 is an elevation, partially in section, of a preferred embodiment of a pothead terminal assembly according to this invention; and

Fig. 2 is a section taken substantially along theline 22 of Fig. 1.

The pothead assembly shown in the drawings comprises a conventional hollow pothead insulator 10 of porcelain or other ceramic. An end closure comprising a cover 11 and a thin-walled cylindrical hood 12, preferably of cop per, is permanently sealed to the upper end of the insulator. To this end, the cover 11 is permanently attached to the insulator by a ceramic-to-metal soldered joint 13; and the hood 12 is permanently attached by solder 14 to the cover. Although the hood 12 and the cover 11 are shown in the drawings as separate parts which are joined together by soldering, it is of course understood that the entire end closure comprising both hood and cover may be made as one integral piece.

The lower end of the cylindrical hood 12 opens (advantageously through a flared neck 15) to the interior of the pothead insulator, and its upper free end is formed with a closure member 16 in which a centrally disposed vent hole 17 is formed. Thus, save for the vent hole, the upper end of the pothead insulator is permanently and tightly closed by a closure assembly which is sealed in place at the factory.

A stem connector 20 comprising an upper stem portion 21 and a cable conductor socket portion 22 is provided. The socket portion 22 of the stem connector is recessed to receive a cable conductor 23. The conductor is bared of its insulation 24 where it enters the stem connector socket recess, and a good electrical and mechanical connection between the stem connector and the cable conductor is provided by filling the recess after insertion of the cable conductor with solder. Laterally extending vents 25 may be formed at the base of the socket portion of the connector to facilitate penetration of the solder into the conductor-receiving recess.

The stem portion 21 of the stern connector is cylindrical and of a diameter only slightly less than the inside diameter of the hood 12. Thus the stem connector may be inserted easily into the interior of the hood. The stem portion 21 is formed with a longitudinally extending slot 26 which, in the embodiment shown in the drawings, extends diametrically of the connector. The free end of the stem portion further is form d with a centrally located tapered threaded recess 27, and a correspondingly tapered threaded'plug 28 is screwed therein. The plug in turn is formed with an axially disposed opening extending completely through it, which adjacent the large end of the plug defines a hexagonal socket 29 of the proper dimensions to receive an Allen wrench, and which adjacent the small-end of the plug is internally threaded to receive a vent hole closure screw 30.

The above-described pothead terminal connection is installed in the field as follows: After the connector 20 has been soldered or otherwise attached to the end of the cable conductor, it is brought up through the insulator and the stem portion thereof is inserted as far as possible into the hood 12. An Allen wrench is then passed through the vent hole 17 into the socket 29 of the tapered plug 28, and the latter is screwed down until the stern portion of the connector has been expanded into tight mechanical and electrical engagement with the hood. Then, after the cable sheath has been wiped in the conventional manner to the pothead body or otherwise attached thereto, sealing compound is introduced through a filling opening in the pothead body below the insulator until the interior of the insulator is completely filled thereby. As the sealing compound rises in the interior of the insulator, air escapes through the slot 26 (the lower end of which extends to below the upper edge of the hood flare and thus communicates with the interior of the insulator) and through the axial opening in the plug 28 and the vent hole 17. When the interior of the insulator has been completely filled with sealing compound, the vent closure screw 38 is inserted and tightened in place. A vent hole washer 32 may be installed under the head of the screw to insure tight closure of the vent hole.

After the pothead insulator has been filled with seal ing compound and the vent hole has been closed with the screw 30, an aerial power line, bus bar, or other conductor may be electrically connected to the pothead terminal by means of a connector 33 formed with an opposed pair of jaws 34, 35 which grip the exterior of the hood 1'2 and are clamped tightly thereagainst by bolts 36.

Since the stem portion 21 of the cable connector is expanded into tight mechanical and electrical engagement with the interior surface of the hood 12 prior to introduction of the insulator sealing compound 31, the latter cannot and does not penetrate between the stem connector and the hood. Hence the risk of a faulty electrical connection between the stem connector and the hood is avoided. Moreover, the stern connector and the cable within the insulator are securely held in their proper position while the sealing compound is being in- -troducedthere is no risk that the stern connector might slip partly or wholly out from within the hood.

Still another advantage of the new assembly is that expansion of the stem connector within the hood prior to clamping the connector 32 about the hood prevents crushing and deforming of the hood when the connector clamps are tightened in place. The hood 12 is preferably made of rather thin gauge copper, and so would be easily deformed and crushed if not fully supported internally by a tightly expanded stem connector. Such deformation of the hood as does occur is in an outward direction due to expansion of the stem connector into tight engagement with it. Since the hood is not crushed or otherwise deformed by application of the connector 32, it is always possible, by reversing the above-described sequence of operations, to recover the pothead insulator with its hood and end closure intact, and to reuse it without having to send it back to the factory or repair shop for refurbishing of the hood or for attachment thereto of a new hood and cover.

I claim:

1. A pothead terminal assembly for a cable conductor comprising a hollow open-ended pothead insulator, a cover permanently sealed to an open end of said insulator, said cover including a thin-walled cylindrical metallic hood extending from and communicating with the interior of the hollow insulator, said hood being substantially closed at its outer end, an extended connector for attachment to the cable conductor, a cylindrical stem portion at one end of said connector of outside diameter only slightly less than the inside diameter of said cylindrical hood and adapted to be inserted fully into said hood up to the substantially closed outer end thereof,

,4 said stem portion having a substantially diametrical slot formed therein extending longitudinally from its outer end, said slot being adapted to communicate at its inner end with the interior of said hollow insulator when said stem portion is fully inserted into said hood, said stern portion also having a tapered recess at its outer end communicating with said slot, and a corresponding tapered threaded plug adapted to be inserted completely into said recess, said plug having a longitudinal opening extending therethrough adapted to communicate with said slot when said plug is inserted into said recess.

2. A pothead terminal assembly for a cable conductor comprising a hollow open-ended pothead insulator, a cover permanently sealed to an open end of said insulator, said cover including a thin-walled cylindrical metallic hood extending from and communicating with the interior of the hollow insulator, said hood being closed at its outer end save for the provision of a centrally located vent hole, an extended connector having a socket portion for attachment to the cable conductor and a cylindrical stem portion at opposite ends thereof, said cylindrical stem portion having an outside diameter only slightly less than the inside diameter of said cylindrical hood and adapted to be inserted fully into said hood up to the substantially closed outer end thereof, said stem portion having a substantially diametrical slot formed therein extending longitudinally from its outer end, said slot being adapted to communicate at its inner end with the interior of said hollow insulator when said stern portion is fully inserted into said hood, said stem portion also having a tapered recess at its outer end communicating with said slot, and a corresponding tapered threaded plug adapted to be inserted completely into said recess, said plug having a longitudinal opening extending therethrough adapted to communicate with said slot when said plug is inserted into said recess.

3. A pothead terminal assembly for a cable conductor comprising a hollow openended pothead insulator, a cover permanently sealed to an open end of said insulator, said cover including a thin-walled cylindrical metallic hood extending from and communicating with the interior of the hollow insulator, said hood being closed at its outer end save for the provision of a centrally located vent hole, an extended connector having a socket portion for attachment to the cable conductor and a cylindrical stem portion at opposite ends thereof, said cylindrical stem portion having an outside diameter only slightly less than the inside diameter of said cylindrical hood and adapted to be inserted fully into said hood up to the substantially closed outer end thereof, said stem portion having a substantially diametrical slot formed therein extending longitudinally from its outer end, said slot being adapted to communicate at its inner end with the interior of said hollow insulator when said stern portion is fully inserted into said hood, said stem portion also having a tapered recess at its outer end cornmunicating with said slot, a corresponding tapered threaded plug adapted to be inserted completely into said recess, said plug having a longitudinal threaded opening extending therethrough adapted to communicate with said slot when said plug is inserted into said recess, and a closure screw adapted to be inserted through said vent hole into said threaded opening in said plug to close the vent hole.

References Cited in the file of this patent UNITED STATES PATENTS 2,089,284 Milliken Aug. 10, 1937 2,279,508 Bergan Apr. 14, 1942 2,593,981 Capita Apr. 22, 1952 2,748,184 Nickolas May 29, 1956 FOREIGN PATENTS 103,877 Australia May 3, 1938 

